In the packaging industry, foil-containing laminates are widely utilized during packaging or package manufacturing. These types of foil-containing laminates include both foil/plastic/paper laminates and foil/plastic laminates. Typically, the foil is an aluminum foil with a plastic including polypropylene, high and low density polyethylene and polyester.
The foil/plastic laminates may be formed into a structure to be used in packaging using either an adhesive to bond the foil/plastic or by resin pellets which are then extruded onto the foil to produce the structure. Typically, the thickness of the metal foil ranges from 0.00025 to 0.002 inches. A typical thickness of the plastic is normally expressed in mils and ranges from 0.5 to 4.0. The ordering of layers in any given laminate may vary depending on the particular packaging application.
Film laminates require an adhesive which can either be a solvent-based material or an aqueous based material. Typically, the papers employed are acid or alkaline bleached pulp.
The manufacture of packages generates a considerable amount of waste material. The waste material coming off a packaging line is either accumulated on a spool or mandrel or shredded into smaller pieces. The collected waste material is then sent to a landfill or incinerated.
With the decreasing availability of space for landfills and increasing cost for use of these landfills, mere disposal of these packaging waste materials is undesirable. Likewise, incineration of these wastes also presents problems related to high cost for incinerator operation due to extensive pollution abatement equipment and resistance by local communities for construction of new incinerator facilities.
In view of the disadvantages associated with landfills and incineration as disposal means for these types of packaging wastes, the prior art has developed numerous techniques for waste material recovery.
In particular, processes have been proposed to separate plastics from other contaminants such as metals or the like. U.S. Pat. No. 4,746,422 to Grimm discloses a method for the separation of a mixture of plastic particles and contaminants by applying a two-phase solution composed of a halogenated hydrocarbon and water to the mixture. The two-phase solution and mixture are rotated in a separator wherein the contaminant having a density greater than the halogenated hydrocarbon is separated by gravitation from the plastic. This method is especially adapted for removing aluminum and/or glass contaminates from plastic bottles and containers. This method is disadvantageous in using halogenated hydrocarbons since they can have adverse environmental effects if allowed to escape from the processing system.
U.S. Pat. No. 4,200,486 to Vagac et al discloses a method and apparatus for reclaiming metals and plastics from scrap paper. This patent utilizes cyclone separators wherein particles of metal foil leave the treatment line in the shape of balls.
U.S. Pat. No. 3,595,741 to Goss teaches a method of reclaiming stock from waste material which utilizes organic solvent extraction followed by solvent removal via distillation. This patent is concerned with fibrous waste material which has plastic or resin associated therewith. No provisions are provided for removing metal in the fibrous waste material.
Flotation techniques have also been employed to separate and/or recover plastics in plastic-containing materials.
U.S. Pat. No. 4,119,533 to Saitoh et al teaches a method of separating highly hydrophobic plastics from a plastics mixture by placing the plastics mixture in an aqueous liquid medium and agitating the medium to float the plastics on the surface thereof to facilitate removal.
U.S. Pat. No. 5,084,135 to Brooks et al discloses another method of reclaiming plastic and cellulosic fiber from plastic coated waste utilizing flotation techniques. The plastic coated waste is subjected to flotation with agitation to separate the plastic from the cellulosic fiber.
U.S. Pat. No. 4,981,876 to Grimmer teaches a process of separating vinyl skin from foam backing by granulating the plastic composite into small chips and mixing the chips with a quantity of water, the mixing step causing the chips to swell and float and separate from the heavier vinyl bits. The separated foam and vinyl are then recovered.
U.S, Pat. No. 4,566,942 to Holz et al relates to a method of treating waste paper, wherein the waste paper is steeped and chemically treated at the same time followed by a density adjustment and sorting step.
U.S. Pat. No. 4,362,600 to Lindstrom et al chemically separates unbleached sulphate fibers from other fibers using high molecular polyalkylene oxides, preferably polyethylene oxide. The patent to Lindstrom et al merely treats waste paper, not waste materials containing metal foil such as aluminum.
None of the prior art discussed above effectively recovers metal foil and the other components from foil-containing laminates used in the packaging industry. Accordingly, a need has developed to provide improved methods and apparatus for the separation and recovery of these types of metal foils that are simple, economical, effective and environmentally sound.
In response to this need, the present invention provides a method and apparatus for the separation and recovery of metal foil, in particular aluminum, and the other components used in these types of laminates. The inventive method and apparatus utilize a polyalkylene glycol polymer solution to form a mixture with the waste material. The mixture is subsequently treated using density variations between the foil and non-foil components to separate and recover all components. The polymer solution and water used in the process can be recycled to eliminate the need for disposal and resupply of additional polymers. Again, none of the prior art discussed above teaches or fairly suggests a method and apparatus for the separation and recovery of metal foils in foil-containing laminates generated as packaging waste.